Volcanic Hazard PDF

DISASTER READINESS AND RISK REDUCTION (Week 6) Volcanic Hazard A volcano is a mountain where lava (hot, liquid rock) comes from a magma chamber under the ground. A volcano usually has a summit, a slope and base. Most volcanoes have a volcanic crater at the top. When they are active, mat...

DISASTER READINESS AND RISK REDUCTION (Week 6) Volcanic Hazard A volcano is a mountain where lava (hot, liquid rock) comes from a magma chamber under the ground. A volcano usually has a summit, a slope and base. Most volcanoes have a volcanic crater at the top. When they are active, materials pour out of it. This includes lava, steam, gaseous compounds of sulphur, ash and broken rock pieces. Volcanoes erupt when magma and pressure come together, and the pressure blows off the top of the solid rock, and the magma pours out. Types of Volcanoes: SHIELD VOLCANOES  Shield or Basaltic volcanoes are built out of layers of lava from continual eruptions (without explosions). Because the lava is so fluid, it spreads out, often over a wide area. Shield volcanoes do not grow to a great height, and the layers of lava spread out to give the volcano gently sloping sides. Shield volcanoes can produce huge areas of basalt, which is usually what lava is when cooled.  Even though their sides are not very steep, shield volcanoes can be huge. Mauna Kea in Hawaii is the biggest mountain on Earth. If it is measured from its base on the floor of the sea, Mauna Kea is even taller than Mount Everest, the tallest mountain on land.  Basaltic / Shield Volcano Eyjafjallajökull, Iceland MT. MAUNA KEA, HAWAII Types of Volcanoes: STRATOVOLCANOES  A stratovolcano, also known as a composite volcano, is a tall, conical volcano. It is built up of many layers of hardened lava, tephra, pumice, and volcanic ash.  Unlike shield volcanoes, stratovolcanoes have a steep profile and periodic eruptions. The lava that flows from stratovolcanoes cools and hardens before spreading far. It is sticky, that is, it has high viscosity. The magma forming this lava is often felsic, with high-to-intermediate levels of silica, and less mafic magma. Big felsic lava flows are uncommon, but have travelled as far as 15 km (9.3 mi). STRATOVOLCANOES MT. FUJI, JAPAN  Types of Volcanoes: CALDERA  A caldera is what is left when a huge stratovolcano blows its top off. It leaves a crater where the top of the volcano was before. Krakatoa, best known for its catastrophic eruption in 1883, is much smaller now.  Collapsed Volcanoes  Magma chamber has emptied and the ground has sunk  Often becomes a lake  New volcanoes can form, or pressure can build from below, lifting the ground  If acidic, this can cause a catastrophic eruption in the form of a ’Super Volcano’  Caldera Volcanoes Mount Pinatubo, MT. KRAKATOA, Phillipines HAWAII  Classification of Volcanoes A traditional way to classify or identify volcanoes is by its pattern of eruptions. Those volcanoes which may erupt again at any time are called active. Those that are now quiet called dormant (inactive). Those volcanos which have not erupted in historical times are called extinct.  Classification of Volcanoes ACTIVE VOLCANOES - An active volcano is currently erupting, or it has erupted in the last 10,000 years. An example of an active volcano is Mount St. Helens in the United States (US). DORMANT VOLCANOES - A dormant volcano is "sleeping," but it could awaken in the future. Mount Rainier in the United States is considered dormant EXTINCT VOLCANOES - An extinct volcano has not erupted in the past 10,000 years. Edinburgh Castle in Scotland is located atop an extinct volcano.  How are volcanoes formed? There are two main processes.  Volcanoes are made when two tectonic plates come together. When these two plates meet, one of them (usually the oceanic plate) goes under the continental plate. This is the process of subduction. Afterwards, it melts and makes magma (inside the magma chamber), and the pressure builds up until the magma bursts through the Earth's crust.  The second way is when a tectonic plate moves over a hot spot in the Earth's crust. The hot spot works its way through the crust until it breaks through. The caldera of Yellowstone Park was formed in that way; so were the Hawaiian Islands. Location Of Volcanoes Layout Of A Volcano  Types of Volcanic Eruption PHREATIC OR HYDROTHERMAL - is a stream-driven eruption, as the hot rocks come in contact with water. It is short lived characterized by ash columns but may be an onset for a larger eruption. Example is Taal volcano eruption in Batangas (as shown on the right)  Types of Volcanic Eruption PHREATOMAGMATIC - is a violent eruption due to the contact between water and magma. As a result, a large column of very fine ash, high speed and side-way emission of phyroclatics called based surges are observed. Example is the eruption of Mt. Fukutoku-Okanoba in Bonin Islands, Japan  Types of Volcanic Eruption STROMBOLIAN - a periodic weak to violent eruption characterized by fountain lava. Example is Mt. Irazu Eruption in Costa Rica  Types of Volcanic Eruption VULCANIAN - characterized by tall eruption colunms that reach up to 20 km high with pyroclastic flow and ash fall tephra. Example is Mt. Paricutin in Mexico.  Types of Volcanic Eruption PLINIAN - excessively explosive type of eruption of gas and pyroclastics. Example is Mt. Pinatubo in Zambales. ACTIVE VOLCANOES IN THE PHILIPPINES Name Province Last Erupted 1 Mt. Mayon Albay erupted at least 51x since 1616 2 Taal Volcano Batangas erupted 33x since 1572 3 Mt. Kanlaon Negros Oriental erupted at least 30x since 1886 4 Mt. Bulusan Sorsogon erupted at least 16x since 1852 5 Mt. Makaturing Lanao Del Sur erupted 10x since 1882 Mt. Calayo or Musuan 6 Bukidnon erupted 2x between 1866 and 1887 Peak Volcano 7 Hibok - Hibok Camiguim erupted 5x since 1827 8 Smith Volcano Cayagan erupted 6x 9 Mt. Banahaw Quezon erupted 3x since 1730 erupted last 1991 w/c was known to be the 10 Mt. Pinatubo Zambales 2nd largest eruption of the 20th century Volcanic Hazard  Volcanic Hazard Tsunami- sea waves or wave trains that are generated by sudden displacement of water (could be generated during undersea eruptions or debris avalanches)  Volcanic Hazard Volcanic Gas - Sometimes gas release is concentrated and toxic to vegetation and people  Volcanic Hazard HARMFUL EFFECTS OF VOLCANIC GASES  Carbon dioxide (CO2) trapped in low-lying areas can be lethal to people and animals  Sulfur dioxide (SO2) is irritating to eyes, skin and respiratory system  Hydrogen sulfide (H2S) is very toxic in high concentrations  Hydrogen halides (HF, HCl, HBr) are strong, toxic acids.  Volcanic Hazard Ash fall - have harmful effects to human health, especially for those who already have respiratory or cardiac diseases/problems. Ash fall can also cause disruption to land and air transportation, water and power supply, communications, drainage canals and sewerage, and can cause damages to buildings, agriculture, and wildlife.  Volcanic Hazard Lahar Hazard  Lahars are flowing thick mixture of volcanic sediments (from the pyroclastic materials) and water, usually triggered by intense rainfall during typhoons, monsoons and thunderstorms.  Lahars can destroy by direct impact (bridges,roads, houses)  Lahars can block tributary stream and form a lake. This can submerged villages within the valley of the tributary that was blocked, there is also the danger of the dammed lake breaching or lake breakout and if this happens, this puts to danger the lives of people in communities downstream  Lahars can bury valleys and communities with debris  Volcanic Hazard Tephra Falls and Ballistic Projectiles Tephra - Includes all sizes of rock fragments and lava blobs ejected into the atmosphere by the force of an eruption which accumulate to form deposits as the airborne materials fall back to earth Ballistic Projectiles - Larger fragments of rock hurled with great force from the volcano  Volcanic Hazard Pyroclastic Flow  A high-density mix of hot lava blocks, ash and gas that propels pyroclastic debris  Gravitational force pulls hot gas and pyroclastic debris down slope from the initial vertical eruption.  VOLCANO PREPAREDNESS  VOLCANO PREPAREDNESS Volcanic alert level system used in the Philippines. The system as shown is used for Mayon, but (with slight variations in wording) is applied to other Philippines volcanoes as well.  VOLCANO PREPAREDNESS Alert Level 0: No Alert. Quiet. No eruption in the foreseeable future. Alert Level 1: Abnormal. Low level unrest. No eruption imminent. Alert Level 2: Increasing Unrest. Moderate unrest. Unrest probably of magmatic origin, could eventually lead to eruption.  VOLCANO PREPAREDNESS  Alert Level 3: Increasing Tendency Towards Eruption. Relatively high unrest. Magma is close to the crater.  Alert Level 4: Hazardous Eruption Imminent. Intense unrest. Hazardous eruption is possible within days.  Alert Level 5: Hazardous Eruption. Hazardous eruption ongoing.  VOLCANO PREPAREDNESS  Permanent Danger Zone (PDZ) is delineated and identified where no permanent habitation is recommended due to the possible impact of various hazards at any time.  VOLCANO PREPAREDNESS HAZARD MAPS  Illustrate potential for ground-based volcanic impacts—lava flows, pyroclastic flows, ash fall, volcanic gases, and more far- reaching hazards (such as lahars) in valleys that drain the volcano.  To help understand the areas that may be affected by specific volcanic eruption phenomena, hazard maps are used. These maps show areas that can be affected and areas that are safe.  Hazard maps are generated for various uses and are most useful in determining risks of living in identified potentially hazardous areas.  Hazard maps can also help people to become aware of specific dangers (lava flow , pyroclastic flows, ash fall, lahars, etc.) they might face in the event that a volcano reactivates.  VOLCANO PREPAREDNESS  VOLCANO PREPAREDNESS (BEFORE, DURING and AFTER)  VOLCANO PREPAREDNESS What To Do Before a Volcanic Eruption (PREPAREDNESS AND MITIGATION)  For longer-term development planning, consult available volcano hazard maps that indicate areas declared as permanent danger zones (PDZs) and areas likely to be affected by different volcanic hazards so that these areas are avoided when choosing sites for developing new residential areas, commercial/ business areas, siting for critical facilities etc.  Be aware of the kinds of volcanic hazards present in your area. Determine the distance of your residence, workplace and livelihood (farms, etc.) from the volcano. Know if you are within what kilometer radius from the volcano summit your location is.  VOLCANO PREPAREDNESS What To Do Before a Volcanic Eruption (PREPAREDNESS AND MITIGATION)  Be aware of the meanings of Alert Levels, and recommended actions. Make sure your family emergency plan has taken this into consideration.  Be aware of community efforts such as identified evacuation areas as well as designated pick up points. Make sure that the whole family knows about this. If you do not plan to stay in evacuation area, and has other alternatives (another house, relatives in another town), make sure that the whole family is aware of this.  VOLCANO PREPAREDNESS What To Do During a Volcanic Eruption (RESPONSE)  Stay inside the house or evacuation area. Do not go sightseeing.  Listen to the radio for advise and information.  If you are outside and very near the volcano, leave the area immediately. If caught in ash fall or tephra* fall, seek shelter immediately. Sometimes, pieces of rocks may be hot, seek care for burns right away.  Do not drive. If you must drive, keep the car windows up and do not operate the air conditioning system as this will bring in ash from outside. Drive slowly as ash fall will reduce visibility. Ash on road surface can cause the roads to become slippery.  VOLCANO PREPAREDNESS What To Do During a Volcanic Eruption (RESPONSE)  Check that your pet or livestock have enough food.  Do not try to clean or shovel the ash fall during eruptions.  Protect yourself from ash fall. I. Close windows and doors to stop the ash from entering the house. II. Turn off all electric fans and airconditioning units. III. Wear dust-mask or cover your face with clean wet towel or cloth to prevent ash from irritating the eyes and entering the respiratory track. IV. Better to use bottled water. If you must use tap water, always boil water first before using.  VOLCANO PREPAREDNESS What To Do After a Volcanic Eruption (REHABILITATION) Listen to the latest update about Alert Levels, other information from the radio. Cook food thoroughly. If the family has evacuated during the eruption, only the adult members of the family should be allowed to go home to inspect the house condition. Only when local authorities- the LGUs have declared that it is safe to go home that the family should return.  VOLCANO PREPAREDNESS What To Do After a Volcanic Eruption (REHABILITATION)  How to Clean Up an Ash Fall: I. As soon as the ash fall has stopped, remove the ash immediately. II. Wear dust mask before you start cleaning. III. The recommended method to clean the ash is to lightly damp the ash so that it does not billow when swept. IV. Clean house roofs first, to prevent damage to gutters and down- pipes. V. Do not dump ash in sewage systems. VI. Inside the house, use damp cloth to remove ash. Avoid vigorous rubbing as ash particles are very abrasive. VII. To remove ash from your car, wash with plenty of water..